Abstract: A message is transmitted on a subcarrier of a main carrier frequency of a radio station. The message is displayed simultaneously with the audible reproduction of the radio program. The message is capable of being displayed dynamically by having different portions thereof sequencing through the display device until the entire message is concluded and/or using a variety of possible display attributes, such as scrolling and flashing. One feature involves scanning the radio band for a station that carries the message. Scanning of a plurality of subcarriers at each station is also performed. One embodiment transmits the message during the "dead time" of other programming normally transmitted on the same subcarrier. The alphanumeric characters of the message are preferably converted prior to transmission into a signal with an average value of zero. The converted characters are decoded at the receiver.

Abstract: A system for decoding a PSK signal comprising a constant amplitude carrier whose phase shifts 180.degree. each time a logical signal is transmitted. The decoder system includes a phase-locked loop including a first phase detector, a loop filter, and a voltage-controlled oscillator. The incoming PSK signal is supplied to the input of the phase-locked loop and through a 90.degree. phase shifter to one input of a second phase detector. The other input of the second phase detector is taken from the output of the voltage-controlled oscillator and the output of the second phase detector will indicate whether a carrier or data is detected. The output of the second phase detector is connected to the inputs of first and second comparators. One comparator has its inputs biased so that it normally outputs a low signal until the second phase detector indicates the detection of a carrier. This output can be used as a source of reconstructed data.

Abstract: A receiver incorporating a phase-locked loop to demodulate a signal comprising a plurality of distinct baseband components is disclosed. The loop filter circuit includes an adjustable resistive element for varying the loop damping factor, thereby providing optimum separation of the baseband components. In addition, the loop filter circuit provides a bandpass high-frequency noise output to a noise-activated muting circuit.